Abstract
We have developed a computer program which can calculate excess path delay for any observation point and for any direction. The program uses data based on the Japan Spectral Model developed by the Japan Meteorological Agency. The data are given at every 3 hours on grid points with separation of about 40 km for 12 layers. We calculated the excess path delay for various observation points in Japan as an example and confirmed that 1) a dry component is in proportion to an atmospheric pressure on the ground with a standard deviation of about 5 mm, 2) a wet component for a path of low elevation angle can be well estimated by multipjying that for 90 degrees by a certain coefficient, 3) the coefficients hardly depend on location though the scattering varies with it, 4) the wet component is hardly related to any single meteorological component on the ground, 5) we can reduce an error in the estimated wet component by using six parameters related to meteorological components on the ground, 6) the error in this estimation of the wet component is about a half of that in the Saastamoinen's model, and 7) it is very difficult to reduce the error for wet weather.
